On the study of the relationship between the thermal stability of Au catalysts and the basic nature of their supports for aerobic oxidation of benzyl alcohol

Abstract

Gold catalysts were loaded on supports of hydrotalcite (HT), MgO, or γ-Al₂O₃ using methods of sol-immobilisation, deposition–precipitation or impregnation. The aim of this work was to study the effect of basic properties of supports on catalytic activity and thermal stability of gold catalysts in the benzyl alcohol oxidation reaction. The structure and property of supports and catalysts were characterized using techniques of X-ray diffraction, scanning transmission electron microscopy, transmission electron microscopy, Hammett indicator, and N₂ physisorption. Gold particles prepared using the sol-immobilisation method were the smallest, the most evenly dispersed, and had the best catalytic activity and lowest thermal stability. Nano-gold catalysts prepared with the other two methods had a lower catalytic activity and a good thermal stability. The thermal stability of gold catalysts varied with the support. The thermal stability of Au/HT and Au/MgO was better than that of Au/γ-Al₂O₃. It was found that the high thermal stability of Au/HT and Au/MgO was ascribed to the basic property of their supports. The finding is instructive in the design of Au catalysts of high activity.